Manufacturers of electronic consumer devices (for example, televisions, radio tuners, home theatre and entertainment systems, digital video disc (DVD) players, video cassette recorders (VCR), compact disc (CD) players, set-top cable television boxes, set-top satellite boxes, video game controllers, home appliances, etc.) typically supply an infrared remote control device along with each electronic consumer device. Such an infrared remote control device is often a handheld battery-powered device with a set of keys and an infrared (IR) transmitter. The remote control device can control the associated electronic consumer device by sending an appropriate infrared operational signal to the electronic consumer device. The operational signal carries a key code. Each such key code corresponds to an associated function of the selected electronic consumer device. Such functions may include power on/off, volume up, volume down, play, stop, select, channel advance, channel back, etc.
If, for example, an individual in the home wishes to increase the volume of a television, then the individual presses the “volume up” key on the remote control device for the television. Circuitry in the remote control device detects the key press condition, accesses appropriate key code and modulation information stored in the remote control device, and uses the key code and modulation information to generate an appropriate control signal that is used to drive an infrared light emitting diode (LED). This control signal causes the LED to transmit the infrared operational signal to an infrared receiver in the television. The key code is carried by the operational signal. The infrared receiver in the television receives the infrared operational signal, detects the key code, and takes an action that is appropriate for the key code. In the present example where the “volume up” key was pressed, the appropriate action is to increase the audio output volume of the television.
A typical user in the home may have many different electronic consumer devices that are to be controlled. A user may, for example, have a digital video disc (DVD) player and a television. To view a movie on a DVD, the user may have to power on and control the DVD with a first remote control device that issues operational signals that the DVD player responds to. In addition, the user may have to power on and control the television with a second remote control device that issues operational signals that the television responds to. It is desired to reduce the number of remote control devices in this situation to one such that a single remote control device is usable to control both electronic consumer devices (the DVD player and the television).
A type of remote control device referred to as a “learning remote control device” may be employed to replace both remote control devices in the exemplary situation described above. The learning remote control device has infrared receiver circuitry as well as conventional infrared transmitter circuitry. The learning remote control device is placed such that the infrared receiver of the learning remote control device can receive infrared operational signals transmitted from one of the remote control devices to be replaced. A key on the remote control device to be replaced is then pressed. The infrared receiver in the learning remote receives the infrared operational signal and stores information about the operational signal such that the learning remote control device can later regenerate the operational signal using the infrared transmitter circuitry of the learning remote control device. This process of detecting and storing information that is usable to regenerate an operational signal is called “learning”.
After the learning remote control device has learned how to regenerate operational signals output from one remote control device to be replaced, the learning remote control device learns how to regenerate operational signals output from another remote control device to be replaced. Thereafter, the user can use the learning remote control device to emulate either the first or the second remote control device. The user controls which of the two remote control devices will be emulated by changing a mode of the learning remote control device. The learning remote control device is therefore now usable to control the both electronic consumer devices in the home, thereby replacing the multiple manufacturer-supplied remote control devices.
The circuitry in the learning remote control device generally includes a microcontroller integrated circuit, an infrared photodiode, and an infrared receiver circuit. The infrared receiver circuit receives a signal from the infrared photodiode and outputs a digital output signal onto a serial input terminal of the microcontroller integrated circuit. The infrared receiver circuit is typically a fairly expensive circuit that consumes a substantial amount of power when it is functioning. Traditional techniques involve realizing the infrared receiver in discrete circuit components (including discrete resistors and/or capacitors) located outside the microcontroller integrated circuit. In one example, the infrared receiver circuit includes multiple operational amplifier gain stages, each including a feedback loop having resistors. The operational amplifier circuit consumes three hundred microamperes or more when it is receiving an infrared signal from an infrared photodiode. In another example, a cascode bipolar transistor amplifier circuit involves multiple resistors and a capacitor in a biasing network. If either of these traditional infrared receiver circuits were to be integrated into the microcontroller integrated circuit, then the resistors and capacitors and/or the complex operational amplifier circuitry would consume an undesirably large amount of die area, thereby increasing the cost of the microcontroller integrated circuit. Accordingly, integrating an infrared receiver circuit onto a microcontroller integrated circuit that is to see general usage in non-learning remote control devices can be recognized to be unacceptably expensive. Moreover, the hundreds of microamperes of power consumed by such a traditional infrared receiver would be undesirable. An improved microcontroller integrated circuit that has an improved, fully-integrated infrared receiver is desired.